Dependence of substrate orientation and etching conditions on the formation of Si nanowires

Silicon nanowires (SiNWs) have received great interest because of their excellent electrical, mechanical, and optical properties as well as their potential applications, ranging from nano/micro-electromechanical system to optoelectronics, and biological/chemical sensors. One of the common methods to synthesize Si nanowire arrays directly from bulk silicon wafers is through electroless etching. This paper investigates the formation of nanowires by electroless etching using a mixture of hydrofluoric acid and silver nitride, in which both anodic and cathodic processes occur simultaneously at the silicon surface. The Ag catalyzes the etching of Si beneath the Ag to form SiNWs. The Ag deposits generated after etching is then removed using a mixture of hydrochloric acid, nitric acid and deionized water (volume ratio 1:1:1) at room temperature. This leads to the formation of well-aligned silicon nanowire arrays. The effect of various parameters such as Si orientation planes, etching temperature and etching duration on the morphology properties of the nanowires is studied using characterization techniques such as scanning electron microscope (SEM).